U-shaped or "gooseneck" traps have long been used in the plumbing industry to prevent backflow of harmful or annoying sewer or pipe gasses into buildings while permitting drainage of unwanted water from floors and other horizontal surfaces. Such traps operate by leaving a small quantity of fluid within the lower portion of a U-shaped trap section to act as a gas barrier. In many applications, however, particularly where access is difficult or where drainage is rare, it is disadvantageous to use such drains. Fluid may evaporate from the trap, permitting free flow of obnoxious gases through the drain; or in some instances the fluids may harden so as to actually block or restrict flow through the drain. Such conventional drains are also relatively difficult and expensive to install. In addition to floor drain applications, these problems are also common to other areas of fluid control, wherever fluid drainage is an occasional problem.
One solution to these problems has been the use of trap primers, which operate to ensure that a minimum level of fluid is left in the drain to act as a trap for gasses which accumulate
Vertically aligned check valves present promising possibilities, as for example as described in my patent application Ser. No. 60/141,913, entitled Check Valve Floor Drain and filed Jun. 30, 1999. However, however, vertically aligned check valves and the like have in some circumstances betrayed a tendency to become fouled by dirt, rocks, and other objects which become caught between the valve stop itself and the valve seat, thus permitting backflow of gasses from within the drain and in some cases retarding or completely blocking drainage of fluid through the valve.
Thus there is need for a simple, economical, and dependable floor drain which will provide efficient operation even when left dry or not called upon to function over long periods of time, and which shows a reduced tendency to become fouled by foreign matter.